Trends in the Incidence of Cancer Among Adolescent and Young Adults in Alberta, 1983–2017: A Population-Based Study Using Cancer Registry Data

Purpose: To describe the cancer incidence burden and trends among adolescent and young adults (AYAs) in Alberta, Canada over a 35-year period. Methods: We obtained data from the Alberta Cancer Registry on all first primary cancers, excluding non-melanoma skin cancer, diagnosed at ages 15-39 years among residents in Alberta from 1983 to 2017. Cancers were classified by using Barr's AYA cancer classification system. Age-standardized incidence rates (ASIR) and the average annual percentage change (AAPC) in incidence rates were calculated. Statistically significant changes in the AAPC during the study period were assessed using Joinpoint regression. Results: Overall, 23,652 incident cases of AYA cancer were diagnosed in Alberta. Females accounted for ∼60% of the diagnoses. AYA cancer increased significantly over the study period overall (AAPC: 0.5%; 95%CI: 0.3%-0.7%), for each sex (AAPC_male: 0.7%; 95%CI: 0.4%-0.9%; AAPC_female: 0.4%; 95%CI: 0.2%-0.6%), and among male and female 20-39 year-olds. Although statistically significant increases were observed in 11 out of 29 cancer sites for at least a portion of the study period, with significant AAPCs ranging from 0.8% (95%CI: 0.01%-1.5%) to 6.6% (95%CI: 4.6%-8.5%), the main driver was thyroid cancer (AAPC: 3.7%; 95%CI: 3.2%-4.2%). Statistically significant decreases were observed for six cancer sites, with AAPCs ranging from -6.4% (95%CI: -8.7% to -4.1%) to -1.1% (95%CI: -1.8% to -0.5%). Conclusions: There is a growing cancer burden among AYAs in Alberta, which is driven primarily by thyroid cancer and early-onset cancers in males. These results highlight the need for etiological studies and tertiary strategies to prevent and mitigate morbidity and mortality in the AYA population.